This Core will be responsible for handling the large-scale genotyping. This Core will be responsible for all the high-throughput genotyping of candidate genes and genetic mapping. Mass Genotyping of individual DNA samples for mapping or association studies of candidate genes will primarily use the TaqMan assay in conjunction with the ABI Prism 700HT Sequence Detection System for single nucleotide polymorphisms (SNPs). In those cases (5-10%) where TaqMan does not work satisfactorily the TaqMan genotyping assay will be supplemented with the Oligonucleotide Ligation Assay (OLA). For high-density SNP frequency mapping of pooled patient samples we will use primer extension in conjunction with denaturing high performance liquid chromatography (DHPLC) detection. The PI's and investigators will identify the autism patients for biological sampling, DNA banking, and genotyping. The Projects, in consultation with this Core, will also determine which genes and SNPs are to be genotyped. In the case of new SNPs, genotype and allele frequency data will be databased and reported to the research community. For genes of particular interest, this Core will provide the necessary DNA sequencing. It will also be responsible obtaining serotonin levels when requested by the Projects.